The ultrastructure and cytochemistry of exocrine secretory cells are being studied. Emphasis is placed upon basic mechanisms of secretion, with particular attention directed toward the role of the Golgi apparatus and lysosomes. The studies are conducted on rat parotid and exorbital lacrimal glands, but other tissues are utilized as necessary. Major areas of investigation are: (1) the role of the Golgi apparatus and GERL in secretory granule formation in resting and stimulated cells, utilizing peroxidase and phosphatase cytochemistry and electron microscope radioautography after injection of labelled glycoprotein precursors; (2) an assessment of the function of GERL, and measurement of cyclic nucleotide levels in secretory cells of the beige mouse, a homologue of the human Chediak-Higashi syndrome; (3) alterations in secretory cells and the role of lysosomes in degradation of secretory material induced by liquid diet or DL-ethionine; (4) the use of exogenous tracers administered via the parotid duct or intravenously to study (a) the fate of endocytic vesicles formed during the removal of membrane from the luminal plasmalemma and (b) the transport of material from the extracellular space to the lumen; and (5) the structure, cytochemistry and distribution of peroxisomes in various tissues. BIBLIOGRAPHIC REFERENCES: Hand, A.R.: Salivary Glands. In Bhaskar, S.M. (Ed.): Orban's Oral Histology and Embryology, 8th edition. St. Louis, C.V. Mosby Co., 1976, pp. 328-360. Hand, A.R.: Ultrastructural localization of catalase and L-alpha-hydroxyacid oxidase in microperoxisomes of Hydra. J. Histochem. Cytochem. 24: 915-925, 1976.